1. Field of the Invention
The present invention relates to methods and systems for managing traffic to and from a host computer, such as a server blade, in response to the active or inactive status of an external switch port.
2. Background of the Related Art
A typical computer system will include a network interface card that allows the computer system to communicate with a network. In a server blade chassis, multiple server blade computers each have at least one pair of network interface cards that are connected to an internal chassis switching system. This chassis switching system communicates with the network through one or more external switching systems. However, if any of the communication links fail or become unavailable, communications from the server blade(s) using that link can become lost.
A virtual local area network (VLAN) is a group of hosts with a common set of requirements that communicate as if they were attached to the broadcast domain regardless of their physical location. A VLAN has the same attributes as a physical local area network (LAN), but it allows for end stations to be grouped together even if they are not located on the same network switch. Accordingly, network reconfiguration can be done through software instead of physically relocating devices.
A VLAN trunk is typically used to carry communications for multiple logical networks over a common physical link. An intermediate Layer 2 switch or bridge device may forward a subset or all VLANs associated with an internal VLAN trunk to an external link. Loss of the external link may thus impact a subset or all of the VLAN traffic (communications) associated with the internal trunk link. It is therefore important to quickly detect the loss of the link and take steps to re-establish communication with the network.
Accordingly, a host computer station may include a firmware agent that periodically issues a TCP/IP ping or an address resolution protocol (ARP) request to a remote target computer station. An active communication will result in a return response. The absence of a return response is an indication to the firmware agent that the path between the host and the remote station is inactive. The firmware agent of the host will then initiate recovery action(s) to redirect outbound traffic to another physical path and continue to test the inactive link to determine when the path to the remote station has been reactivated. Although this method is typically used to detect loss of a physical path, it is also applicable to loss of a logical path, such as through an intermediate router or gateway. Loss of the path is implied by absence of a response from the remote station.
Patent Publications US 2006/0206602 and US 2006/0203715 describe a method and system that redirects traffic from a server blade to different access switches that each provide data communication with a network. The server blade has a primary interface associated with a first access switch and secondary interface associated with a second access switch. Each access switch has external ports directed toward a network, and corresponding internal ports directed toward the server blades. In the event that a first access switch loses a data signal or connection at one or more of its external ports, the corresponding internal port(s) is (are) automatically disabled. The disabling of the internal port causes the primary interface in the server blade to failover to the secondary interface that is coupled to the second access switch.